Heating apparatus having simplified focussing means

ABSTRACT

Heating apparatus including a radiation source and reflector means for focussing reflected rays at an image focus. The source of radiant energy and reflector means are mounted upon an adjustable support which is linearly movable in a vertical direction to position a heating apparatus above a working surface. The working surface is comprised of means movable in two mutually perpendicular directions within a plane perpendicular to the direction of movement of said heating apparatus. Said means is further adapted to receive and support the object to be heated. Indicator means located outside of the heating area, is coupled to the heating apparatus and includes pointer means adaptable to be positioned immediately above the region of the object to be heated. The support assembly is initially moved to a first position. The object to be heated is placed upon the supporting means which, together with the eating apparatus is adjusted to place the indicator so as to rest upon the object to be heated. After adjustment, the supporting apparatus is then moved to a second working position whereby the adjustments previously made rapidly and accurately locate the object to be heated exactly in the focal image of the reflector means. Further means may be provided for locking the supporting surface in position to prevent its jarring when moved into the working position. Also, novel reflector means may be provided for projecting the object being heated upon a screen for viewing purposes to accurately control the level of heating required whereby the radiation employed for heating is utilized as the illuminating source for the projection apparatus.

Cl H. l

[ May 9, 1972 Elam 3,661,369

unuou umauib 1' ill Costello l 54] HEATING APPARATUS HAVING SIMPLIFIEDFOCUSSING MEANS [72] Inventor: Bernard J. Costello, Ringoes, NJ. [73]Assignee: Argus Engineering Company, Inc.,

8 Hopewell, NJ,

l [22] Filed: May 1, 1970 l 21 Appl. No.: 33,725

[52] U.S. Cl ..263/2 R, 263/6 R, 263/40 R [51] Int. Cl ..F27b 9/14, F27b3/06 [58] Field ofSearch ..263/6 R, 2 R, 40 R [56] References Cited UNlTED STATES PATENTS 1,810,643 6/1931 Colby ..263/2 R 2,026,370 12/1935Winkler ..263/40 R 2,457,654 12/1948 Furkert ..263/6 R 2,519,616 8/1950Watkins..... 263/40 R 3,151,851 10/1964 Negley ..263/40 1 PrimaryExaminer-John J. Camby Auornev-Ostrolenk, Faber, Gerb & Soffen 57 1ABSTRACT source of radiant energy and reflector means are mounted uponan adjustable support which is linearly movable in a vertical directionto position a heating apparatus above a working surface.

The working surface is comprised of means movable in two mutuallyperpendicular directions within a plane perpendicular to the directionof movement of said heating apparatus. Said means is further adapted toreceive and support the object to be heated. lndicator means locatedoutside of the heating area, is coupled to the heating apparatus andincludes pointer means adaptable to be positioned immediately above theregion of the object to be heated. The support assembly is Further meansmay be provided for locking the supporting surface in position toprevent its jarring when moved into the working position.,Also, novelreflector means may be provided for projecting the object being heatedupon a screen for viewing purposes to accurately control the level ofheating required whereby the radiation employed for heating is utilizedas the illuminating source for the projection apparatus.

17 Claims, 13 Drawing Figures PATENTEDMAY 91912 2,661,369

SHEET 3 BF 3 EEEE- BACKGROUND There exists a wide variety ofapplications wherein it is extremely important to provide precisionheating of materials. For example, there are various operations employedin the construction of dental prosthetics which require such precisionheating. Such operations include high temperature brazing, soldering,coating of dental implants with ceramic, and melting of metals forcasting of teeth. The reference to precision implies control of both thesize of the area heated and the temperature to which the workpiece isexposed.

Historically, several methods have been employed by dental techniciansand other like operators to perform these tasks. The most commontechnique is one in which a hand-held torch that is completelycontrolled by the operator is employed for such precision heating. Othermethods include induction heating, resistance heating, and furnace andelectrical arc heating. No one method has been found effective inperforming all of the operations previously mentioned. Therefore, thepractice in the dental industry is to rely upon central laboratories toperform most of the services required. Such laboratories, which usuallyserve a large number of clients, are in a position to warrant this rangeof equipment since the demand for use of each system is spread over alarge number of customers.

This practice is uneconomical for the dental practitioner, not so muchin a direct cost sense, but more as a result of the inconvenience ofhaving to deal with a vendor (i.e., a dental laboratory) engaged in sucha craft oriented function. The dentist loses control over the quality ofthe implant. Also the time involved in preparing and sending materialsand specifications between the parties is excessively long if theinterest of the patient is to be best served.

Also, it is quite often necessary to repair, or change implants on veryshort notice. If the part in question must be returned to the laboratoryfor such services, the patient is further inconvenienced by stillanother return visit to the dentist. The operation could be performed inthe office, in

many cases, if a general purpose, broadly applicable heating device wereavailable.

THE PROBLEM lt is therefore desirable to provide a system for performingvarious heating operations necessary in the construction of dentalprosthetics. Such a system or systems ideally must meet the followingcriteria;

1. The system must be capable of performing precision heating operationsas will be more fully described in this application.

2. The system must minimize dependence upon operator skill forsuccessful operation.

. The system must be capable of quick conversion from one type ofoperation to another.

4. The system must be convenient to operate and require a minimum ofunderstanding. I

5. The system must perform the operations to be described in detailhereinbelow in rapid sequence. That is, the operation may be performedin a series of short steps, and, in an uninterrupted manner.

. The system must preferably be within a cost range that will notrequire intense and repeated use to amortize or justify the need forsuch a piece of equipment in the average dental office.

LAJ

OPERATIONS PERFORMED Several operations employing precision heating arewidely used in the construction of prosthetics. The most common are:

high temperature soldering of metal tooth crowns; glazing of ceramiccoatings on crowns; and melting of metals for irivestment casting ofcrowns.

HIGH TEMPERATURE BRAZING OR SOLDERING J tually occupy when implanted inthe patients mouth. This is done by making a wax impression of the teethto be capped, after they have been prepared for capping. The impressionis used to make a ceramic base, that is, a replica of the teetii; from acastable material.

This replica, which is identical to a portion of the patients mouth,holds the crowns in the exact relative spacing. Quite often, dovetailsare made in adjoining crowns to aid in location. In its simplestembodiment, a small gap is left between the crowns in order to accept afiller alloy that is compatible with the metals in which the crowns tobe joined are made. A sliver of the filler alloy is placed between thecrowns and melted. The filler alloy flows between the crowns bycapillary action to form a sound and firm connection.

The materials normally employed in such operations are usually noblemetals and/or their alloys. Occasionally, a fluxing agent such asphosphorousmay be added to the alloy to aid in wetting the alloy to themetals of the crowns being joined.

Several important factors must be controlled in the soldering operationsto make it both feasible and acceptable. The

first of these is the preservation of the shape of the crowns andreplica must be remade from the start. Therefore, the

procedure is not only expensive but is time consuming.

Damage to the crowns while soldering may be the result of any one of avariety of mishaps, the most obvious of which is overheating.

The cast tooth is an alloy of noble metals and small amounts of basemetals. If the crown is even moderately overheated, the base metals willburn and change the surface condition of the casting. In some alloysthis will be found to occur even though melting does not occur.

Obviously, the next degree of damage, the change in the surface, isgross deformation due to melting. Once melting occurs the casting is,for all practical purposes, destroyed and must be remade.

A more subtle problem which occurs in joining crowns is that ofmaintaining the correct spatial relationship between the crowns so thatthey will fit the tooth stubs remaining in the patients mouth.Displacements of as small an amount as 0.005 inch can cause severe painto the patient after the implant is in place.

The last significant hazard is that which may occur to the ceramicreplica used to hold the crowns while soldering. Whereas the replica isnot normally reused, it is desirable to keep the replica intact in theevent of an accident in later steps of the implant construction process.Thus, saving the replica for reuse clearly avoids the necessity formaking a new one, if required.

u CERAMIC COATING OF CROWNS Once a crown or group of crowns isconstructed, the appearance of the crown in the patients mouth isimportant if it is visible. For this reason, a coating (overlay) isoften applied to the crown. This coating performs a cosmetic function aswell as being a surface preparation to make the tooth look and feel morenatural. Great pains are taken to color and stain the coating so as toappear as natural as its real neighbors in the final grouping within themouth.

Two general types of coatings are used for this purpose plastic andceramic. Both coatings are applied as slurries to the prepared crown andthen fused in place by heating. The fused micro-surface of the coatingis smooth and enamel-like. The macro texture and color is dependent uponthe skill of the technician in applying the slurries to the crowns. Theideal result is a tooth surface that cannot be distinguished from thereal thing.

Ceramic coatings will be described in greater detail hereinbelow. Ascompared to plastics, such ceramic coatings are much more difficult toapply properly but are also found to be more durable and attractive.

Two techniques for the application of ceramic coatings are presentlyemployed vacuum firing and air firing. It is generally agreed thatvacuum firing produces the most dense and tenacious coating. The airfiring technique is more convenient, and less elaborate equipment isrequired.

INVESTMENT CASTING The last significant area of application which is ofinterest consists of the technique for melting small quantities of alloyfor investment casting of crowns and like structures.

Investment casting is an ancient art requiring several very criticalsteps. Since a complete description of the investment casting process isconsidered to be beyond the scope of the present invention, only thoseaspects which have immediate bearing will be discussed hereinbelow.

In performing the technique, a prepared mold which is usually a shell ofa ceramic-like material, is produced. The inside surface of the mold isthe negative" of the part to be cast. The molten metal is poured intothe shell and allowed to cool. The shell is then broken away to recoverthe casting.

Investment casting is a one-time process since the mold is expended anduseless after performing its function. Therefore, high reliability andhigh yield are imperative if the best economy and service are to beachieved.

Several factors determine the quality of the casting, temperature levelis very important in that it determines the fluidity and integrity ofthe alloy. It is typically desired to hold the melt temperature within arange of: 2 percent of optimum temperature.

Another factor to be considered is the method used to force the metalinto the mold. Three common methods which are presently in use aregravity, vacuum and centrifugal force. In certain cases, one or more ofthese methods are often combined to achieve a desired effect.

SOLUTION TO THE PROBLEM I have invented a facility for performing all ofthe above desired operations, which facility has the versatility andsimplicity to fulfill all of the aforementioned criteria. The facilityutilizes focused radiant energy as a heating source. The enormousversatility and advantages of focused radiation will become obvious uponconsideration of the detailed description of the invention which is setforth hereinbelow.

The facility I have invented is adaptable to high temperature soldering,overlay firing, and investment casting of prosthetics, as well as othersimilarly related applications which require precise heating of a welldefined area or region and precise control of the temperature level andduration of exposure to heating. All of the operations describedhereinabove may be performed in air, a controlled atmosphere, or in avacuum.

The invention is comprised of a high intensity source of radiant energypositioned at the primary focal point of a reflector. All energy fromthe radiant source that strikes the reflector is directed to a point inspace hereinafter referred to as the secondary focus. Any absorbingobject placed at the secondary focus will become hot by radiant heating.The reflector and radiant energy source are mounted upon an adjustablesupporting structure which is adapted to permit the source and reflectorto be moved either upwardly or downwardly substantially along animaginary vertical line. This structure is positioned above a supportingsurface assembly for positioning and supporting an object to be heated.The object supporting assembly is movable along guiding means betweenfirst and second stops and is further capable of being moved in mutuallyperpendicular directions in an horizontal plane. An indicator memberhaving a suitable pointer at is free end is mechanically connected tothe structure which includes the radiant energy source and reflector.

In operation, the object supporting means is moved away from thereflector and radiant energy source until it reaches the first stopmember. The object to be heated is then placed upon the supportingsurface assembly and the reflector means is adjusted until the pointerfree end is positioned immediately above the area to be heated. Furtheradjustment may be made by moving the supporting surface means in ahorizontal plane until the area to be heated is immediately beneath thepointer member.

After the aforementioned adjustment procedure, the supporting surfacemeans is moved toward the reflector and radiant energy source andagainst the second stop member whereby the physical relationship betweenthe pointer, the second stop means and the radiant energy source andreflector is such that the object to be heated is precisely positionedwithin the image focal point of the reflector. Energizing the radiantenergy means over a prescribed time period provides the necessaryheating which is constrained to only that area of interest.

In applications where it is desired to provide a "line" of radiantenergy, a line heater in the form of an elongated reflector may beemployed. In such applications, the pointer may take the form of anelongated pointer bar representing the imaginary line focal zone or,alternatively, may take the form of a pair of spaced pointers whose tipsrepresent the ends of the imaginary line focal zone.

Vacuum means may be combined with the supporting surface assembly forfirmly locking the supporting surface means into position immediatelyafter adjustment thereof. The vacuum means may also be employed inconjunction with an enclosing chamber member for those applicationswherein it is desired to perform the heating operation in a vacuum orcontrolled atmosphere.

A viewing apparatus may also be provided for facilitating observation ofthe immediate area being heated wherein said viewing apparatus utilizesthe radiant energy for heating as the illumination source for projectingthe area of interest upon a viewing screen. i

A crucible, having two crucible halves each pivoted upon a pair ofknife-edge supports, is provided with a fusible element forautomatically separating the halves of the crucible when the charge ofmaterial within the crucible reaches the desired temperature level.Radiant heating positioned above the crucible and directed downwardlytoward the crucible assures good uniform heating of the charge containedin the crucible before the fusible material is melted to permit themolten charge to be dispensed into a mold or other suitable container.

It is, therefor, one object of the present invention to provide a novelradiant energy heating means including means for rapidly and accuratelylocating the object to be heated precisely within the secondary focus ofthe heating apparatus.

Another object ofthe present invention is to provide a novel method andapparatus for precisely heating an object wherein the region to beheated may be simply and accurately controlled by providing means forrapidly and accurately positioning that portion of the object to beheated within the image focus of the radiant energy source.

\Still another object of the present invention is to provide a novelradiantly heated crucible assembly having a fusible element forautomatically dispensing a charge of material when the material iselevated to the desired temperature level.

The present invention relates to novel radiant energy heating apparatuswhich includes projection means for projecting an image of the area ofinterest being heated in which the radiant energy source serves the dualfunctions of providing the necessary radiant heating and providingsufficient illumination for the projection system.

These as well as other objects of the present invention will becomeapparent when reading the accompanying description and drawings inwhich:

FIG. 1 is a basic schematic view of a radiant heating system.

FIG. 2-is a perspective view showing the heating apparatus designed inaccordance with the principles of the present invention.

FIG. 2a shows an elevational view of sembly ofFIG. 2.

FIGS. 2b and 2c are perspective views showing alternative embodimentsfor the mechanical pointer of FIGS. 2 and 2a which may be employed inconjunction with line focal images.

F IG. 3 shows and elevational view of a portion of the apparatus of FIG.2 modified for heating objects in a vacuum.

FIG. 3a is a top view showing the gasket assembly which may be employedin the embodiment of FIG. 2 for locking the work plate relative to thesubplate.

FIG. 4 is an elevational view of a FIG. 2 which is adapted to includeparatus.

FIG. 5 is an elevational view showing a portion of the apparatus of FIG.2 and adapted to perform the operations associated with investmentcasting.

FIGS. 6a and 6b are top and elevational views respectively of anassembly which may be employed to permit the work late to move inmutually perpendicular directions relative to the sub-plate, whichcomponents are employed in the apparatus of FIG. 2.

FIG. 7 shows a portion of the investment casting apparatus of FIG. 5 ingreater detail.

FIG. 7a shows an alternative crucible embodiment which may be employedin place of the crucible embodiments of FIGS. 5 and 7.

A general description of focused radiant heating systems is portion ofthe apparatus of projection and viewing apset forth in US. Pat. No.3,469,061 and copending applica tions Ser. Nos. 710,546, filed Mar. 5,1968 now US. Pat. No. 3,522,407 and 872,232, filed Oct. 29, 1969 nowU.S. Pat. No. 3,609,283.

Very briefly, the present invention, FIG. 1 shows such a focusedradiation system as being comprised of a high intensity source ofradiant energy 10 which is placed at the primary focal point of areflector 12 whose concave surface 11 is highly reflective to radiantenergy emitted by the source 10. All energy from source 10 which strikesthe reflector, i.e., rays 14a and 14b, for example, is directed to apoint 13 in space which will hereinafter be referred to as the secondaryfocus. Rays 15a and 15b, respectively, represent the rays 14a and 14bafter they have been reflected and directed toward the secondary focus.Any absorbing object placed at the secondary focus will become heated bythe radiant energy striking the object. A supporting surface 16 may beprovided for positioning and supporting the object to be heated at theproper location relative to the focused radiant energy apparatus.

The facility of the present invention is shown in greater detail in FIG.2 and the initial description set forth hereinbelow shall bespecifically related to the locating and focusing means developed toprovide simple and accurate placement of the radiant heating system.

In working with focused radiation on irregular shapes, the major problemis that of positioning the object so that the portion of the object tobe heated is located within the focal zone a portion of the asand forpurposes of sufficiently understanding downwardly in the Z axis. Radiantsource irregular and non-repetitive shapes at the secondary focus ofwith relatively good accuracy. The problem arises due to the fact thatthe radiation, or light, is invisible until it strikes the work piece.Also, the light is extremely intense thereby making it uncomfortable toobserve without very dark glasses.

to define the zone. The types of structures being heated in dental workare not typically large enough, flat enough or suf ficiently uniform toprovide an effective focusing surface, thus rendering this techniqueunreliable and impractical.

The latter technique, that of mechanical pointers, is inconvenient aridcumbersome to use. In focused radiant energy systems, the most effectivereflector is one that has the shortest focal length and largest possiblediameter. Of course there are practical limits to each of theseparameters, but each tends to restrict observation and manipulation inthe focal zone. The introduction of a mechanical pointer into theheating region further restricts the zone and makes the operation muchmore tedious and difficult.

The apparatus [have invented utilizes a mechanical pointer which ispositioned well outside of the heating system, thereby allowing completefreedom of manipulation and observation in the placement of the workpiece.

The apparatus is shown in FIG. 2 and includes the radiation source 10and reflector 12 which may, for example, be an ellipsoid of revolution.These components are fixedly mounted to a rack member 17 which isslidably mounted relative to a stationary post 18 having its lower endsecured to a surface 19. Post 18 is adapted to provide for slidablemovement between stationary post 18 and rack member 17. A gear member 21is pivotally mounted to stationary post 18 by any suitable means and hasan extending shaft 22 provided with a manually operable control knob 23for rotating gear 21 which meshes with the rack member 17 to move rackmember 17 and hence radiation source 10 and reflector 12 either upwardlyor 10 and reflector 12, however, are fixed in the X and Y directions soas to be prohibited from movement in the X-Y planes.

A pointer assembly 24 has a first end thereof secured to the reflectorassembly 12 and is provided with a pointer 25 at its free end fordefining an imaginary focal point 13' which lies in a horizontal planeparallel to the X, Y plane that also contains the true secondary focus13. The imaginary focal point 13' is displaced from the true secondaryfocus by a distance D measured in a horizontal plane and which distancelies along a line parallel to the X axis. The pointer may be hinged,i.e., pivotted, to the reflector means by means of a suitable bracket 26secured to the reflector l2 and adapted to receive a pin 27 forpivotally mounting the pointer to the bracket. Pointer arm 25 isprovided with a suitable opening (not shown) to receive pin 27. Anadjustable threaded screw 28 may be provided to engage a secondvertically aligned tapped opening 29 in arm 24 to permit adjustment ofthe pointer 25 to lie in the same horizontal plane as the actualsecondary focus 13. The pointer may alternatively be either hinged orarranged to be completely removable from reflector 12 for convenience.

A subplate 30 is mounted to be movable in the X direction by a pair ofguide rails 31 rigidly secured to surface 19 and free to move along theX axis through the distance D which corresponds to the displacementbetween the true secondary focus 13 and the imaginary secondary focus13. This movement is limited by stops 32 and 33 which are positioned inthe path of movement of subplate 7 and which may be made adjustable, ifdesired, to provide for readjustment and realignment of the apparatusfor purposes to be more fully described.

e The plate 34 which constitutes the work plate upon which a work pieceis supported, is movably mounted upon subplate 30 so as to be enabled tomove in the XY plane. Subplate 30, however, is free to move onlylinearly in either a forward or rearward direction along the lineparallel to the X axis due to the constraints placed upon the subplatemovement by the supporting rails 31. The extent of said movement islimited to the distance D.

In operation, the work plate 34 containing a work piece 35, is placedupon the subplate 30. Subplate 30 is pushed against stop member 32.Preferably, the heat source and reflector assembly is moved verticallyupward in a direction parallel to the Z axis so as to provide sufiicientclearance for placement of the work piece and work plate 35 and 34,respectively, beneath the pointer assembly 24. Manually operable handle23 is then manipulated so as to bring the pointer to the same level (orheight) as the portion of the work piece 35 which is to be irradiated.Work plate 34 is then adjustably maneuvered in the X Y plane so as toplace the area of the work piece to be heated beneath the tip 25 of thepointer assembly 24. In this position, the portion of the work piece tobe irradiated is located at the imaginary focal point 13'. Obviously,the pointer and reflector assembly may be moved downwardly either beforeor after manipulation of work plate 34. The adjusting mechanism forassemblies 10, 12 and 24 is preferably operated so as to bring the tip25 of the pointer to a position about one-sixteenth inch above the areato be heated upon the work piece.

Since points 13 and 13 lie in the same plane, and this plane iscontrolled by the Z direction mechanism (i.e., the mechanism forlocating the assemblies l0, l2 and 24 in the vertical direction), thetrue focus is always at the same relative level as the imaginary focus,and is represented by the tip 25 of pointer assembly 24.

As was mentioned hereinabove, adjustment of the work plate within theX-Y plane, brings the area to be heated directly beneath the pointer 25.This is done without moving the subplate which has previously been movedto abut stop member 32. The downward adjustment of the pointer tocontact the center of the zone to be heated exactly locates theimaginary focal point upon the surface of the work piece to beirradiated.

The pointer may then be either removed or pivoted upward and away fromthe work piece. The work piece is now accurately positioned in theimaginary focus and may further be conveniently handled or operated uponfor further preparation, such as alloy placement, fluxing, orapplication of overlay material. The full significance of the apparatusand procedure will become apparent upon still further discussion of theoperations and other ancillary features which are capable of beingachieved by the apparatus.

The final step consists of moving subplate 30 away from stop member 32and into engagement with stop member 33. This places the work plate 34and work piece 35 within the heating zone, with the precise portion ofthe work piece to be irradiated being located within the true focal zone13. The source may then be energized to perform the heating operation.The entire sequence, including all placements and adjustments, can beperformed in a period well under 1 minute. The simplicity of theapparatus resides in the fact that the work piece and work plate, oncepositioned immediately beneath the tip of pointer assembly 24 is veryaccurately moved a distance D by movement of subplate between stops 32and 33. Deviation in the direction lateral to this movement (i.e., inthe direction substantially parallel to the Y axis) is totallyeliminated and constrained by the guide rails 31. Accurate pre-alignmentof pointer 24 relative to the true focal zone exactly locates thepointer tip 25 lying in the same horizontal plane as the true focal zone13 and to be a distance of exactly D removed from the true focal zone.Accurate positioning of stops 32 and 33 assure movement of subplate 30and hence work plate 34 and work piece 35 the distance D.

As an obvious alternative, the work plate 34 may be omitted entirely andthe top surface of the subplate may be employed for supporting the workpiece 35.

In applications in which the region to be radiated is a line" image, theradiant energy source 10, shown in FIGS. land 2, may be comprised of anelongated energy source positioned at the first focal point as shown inFIG. 1, which is to be used in conjunction with an elongated reflectorassembly such as, for example, the line energy source and reflectorassembly of FIGS. 2-4 shown in patent application Ser. No. 774,898,filed Nov. 12, 1968 and assigned to the assignee of the presentinvention. Similarly, the line heater may be of the type sold by theArgus Engineering Company, identified as Model 91 in a brochure entitledConray Basic Models" printed and distributed by the Argus EngineeringCompany. Sincethe radiant energy is reflected to form a line image, themechanical pointer is likewise modified so as to take the form as shownin FIGS. 2b and 2c, for example. FIG. 2 b shows a pair of mechanicalpointers 24a and 24b each being secured to the line reflector l2 andhaving their pointer tips 250 and 2512, respectively, lying along animaginary straight line 13" which represents the imaginary focal linewith the tips 25a and 25b defining the end points of the line. Asanother alternative, the mechanical pointer may take the form of apointer arm 24c having an elongated bar 24d secured at its free end withthe bar being tapered to form a knife-like head 24e along the bottom ofbar 24d to represent the imaginary focal line which is substantiallyparallel to the true image focal line formed by the reflected radiantenergy from reflector 12'.

As another alternative, the adjustable assembly of FIGS. 61: and 6b maybe employed. As shown in these two figures which are top and end views,respectively, of the subplate 30 and the work plate 34 includingthe-adjustable assembly, the under surface 34a of work plate 34 isprovided with first and second pairs of rollers 81-82 and 85-86, whichrollers are secured to the under surface 34a by pins such as, forexample, the pins 83 and 87 shown in FIG. 6b. The pair of rollers 80 and81 which are rotatably mounted upon pins 82 and 83, shown best in FIG.6a, are arranged to be rollably received within a channel member 70. Theroller members 84 and 85 are arranged to be rollably received within achannel member 71. As shown best in FIG. 6a, channels 70 and 71 arearranged in spaced parallel fashion. The underside of channel 70 hassecured thereto a pair of pins 74 and 75 which pivotally mount a pair ofrollers 72 and 73, respectively. Channel member 71 has secured thereto apair of pins 78 and 79 which pivotally mount roller members 76 and 77,respectively. The roller members 72 and 76 pivotally mounted to channels70 and 71, respectively, are reliably received within an elongatedcavity 30b provided in the top surface of subplate 30. Rollers 73 and77, which are pivotally mounted to channels 70 and 71, respectively, arerollably received within a second elongated groove 30a provided in theupper surface of subplate 30. The elongated grooves 30a and 3022 arearranged in substantially spaced parallel fashion.

In operation,. the work plate 34 may be rolled in the direction shown byarrows 88, causing the roller pairs 8081 and 84-85 to roll along thechannels 70 and 71, respectively. Work plate 34 may be moved in thedirection shown by double-headed arrow 89 whereby the rollers 72-76 and73-77 will move within the depressions 30b and 30a, respectively,

thereby enabling work plate 34 to move in mutually perpendiculardirections relative to subplate 30. The rollers may be adapted to fitsnugly within their cooperating members to prevent accidental movementof the work plate after the work piece is aligned relative to thepointer.

The work plate may be lifted off the subplate at any time in cases whereit is desired to mount a fragile work piece upon the work plate at aremote location or to perform subsequent operations upon a work piece ata remote location.

In applications where the alignment of the work piece need not beextremely precise, the stop 32 may be omitted (or it need not bepositioned exactly the distance D plus the length of the subplate fromstop 33) and the work plate or subplate (if the work plate is omitted)may be provided with a guideline 34g. By aligning the region of the workpiece to be irradiated directly above the guideline 343, the region tobe heated will thus be positioned in the true focal image of thereflector with a reasonable degree of accuracy when the plate 34 ismoved against the stop 33.

FURTHER REF INEMENT AND FEATURES Several of the operations mentioned fordental work are best performed in a vacuum environment. The adaption ofa vacuum feature to the above described system has been found to besimple and convenient. Furthermore, the vacuum system has been found toprovide an advantageous locking feature which may be employed betweenthe subplate and work plate and which is very valuable even in instanceswhen a vacuum environment is not being employed.

FIG. 3 shows a portion of the system of FIG. 2 wherein like elements aredesignated by like numerals. As shown in FIG. 3, work piece 35 ispositioned upon work plate 34 and is covered with a bell jar-type 36 ofenclosure. The bell jar is preferably formed of a radiation transmissivematerial such as quartz, Pyrex, or Vycor. The work plate 34 is providedwith an annular-shaped recess 34a for receiving a sealing gasket 37which is obviously resilient so as to permit the marginal edge of belljar 36 to be urged into firm, airtight, sealing engagement with thegasket as a result of evacuation of the hollow interior region definedby work plate 34 and bell jar 36. The sealing gasket is preferablyformed of a non-radiation absorbing elastomer such as clear siliconerubber or the equivalent.

A gasket 38 is also provided between work plate 34 and subplate 20,which gasket 38 is also shown in FIG. 3a wherein the configuration ofthe gasket is designated by the phantom lines of FIG. 3a which representthe exterior and interior peripheries thereof. Gasket 38 permits thefreedom of movement of work plate 34 relative to subplate 30 in order topermit the work piece 35 to be placed in the appropriate heating zone byinitially adjusting the plate to place the work piece 35 beneath thepointer in the same manner as was described hereinabove.

When the interior region mentioned hereinabove is evacuated, thesub-atmospheric pressure between plates and 34 causes the plates to berigidly held in position relative to one another. It has been found thatthe atmospheric holding force is more than sufficient to join bell jar36 to work plate 34 and to join plates 34 and 30 into a very rigidassembly which is not easily displaced.

Appreciation of the function of gasket 38 can best be understood from aconsideration of FIG. 3a in which work plate 34 is shown as beingdisplaced toward the right relative to subplate 30 by a distance a andis further shown as being displaced by a distance d in the positivedirection of the Y axis.

In order to evacuate the hollow interior region between bell jar 36 andwork plate 34, subplate 30 is provided with an elon gated opening 39whose right-hand end is coupled through a suitable coupling assembly 40to conduit 41 and whose lefthand end opens in the upper surface ofsubplate 30. Work plate 34 is provided with a vertically aligned bore34b which communicates with the upper and lower surfaces of the workplate. Conduit 41 is provided with a valve 42 for selectively couplingor decoupling a vacuum pump with conduit 41.

In the case where the heating operation takes place in the vacuum, thevacuum pump source (not shown for purposes of simplicity) connected toconduit 41 causes the interior region between bell jar 36 and work plate34 as well as the interior region defined by the lower surface of workplate 34, the upper surface of subplate 30 and gasket 38 to be evacuatedwhen valve member 42 is opened. Once the desired vacuum condition isachieved (which may be determined by providing a gauge 43 in the vacuumline), valve 42 may then be closed and the vacuum source may bedeenergized. Obviously, the ap paratus may further be employed in vacuumsystems where the vacuum source is continuously operated in order tomaintain a desired evacuation.

In applications wherein it is desired to merely lock work plate 34relative to subplate 30 and wherein no vacuum environment is requiredduring the heating operation, a suitable plug 44'may be inserted (forexample, threadedly engaged) into bore 34b so as to seal this opening.The vacuum source may then be coupled to conduit 41 by opening valve 42so as to evacuate the hollow interior region defined by the lowersurface of work plate 34 and the upper surface of subplate 30 and gasket38. Only a small negative pressure level is required to maintain thesetwo plates in their relative positions. Obviously, the evacuationoperation is performed after work plate 34 and hence work piece 35 arepositioned relative to the pointer assembly 24.

It has been found to be desirable in some casesto introduce aback-filling gas, such as hydrogen, while the vacuum chamber is beingevacuated. This may be performed in the present invention by providing avent hole 45 in work plate 34 which, at its left-hand end, is coupledthrough conduit 46 and HEATING OBSERVATION FEATURE Visual monitoring ofthe heating operation is vital especially in the case of dentalpreparations since each part has rather unique heating properties andcharacteristics. It is impossible to effectively assign time-powerparameters to mechanically control the heating cycle. It isoftennecessary, therefore, for the technician (or other operator) to manuallycontrol the power level of the source as well as controlling the ON-OFFfunction.

Radiant heating, as described herein, is accompanied by a verysignificant amount of visible radiation. This visible light is sointense that it is impossible to visually monitor the operation beingperformed without the use of some aid or protective means. I haveemployed two observation aids on the described apparatus: filters andoptics.

The filter may be simply a dark plastic, or glass, lens that absorbsmost of the radiation. The filter may be hinged to the front of thesystem for convenience. For example, as shown in FIG. 2, a filtercomprised of flat sheet 50 is coupled to one arm 51a of an elongatedhinge 51 whose other arm 51b is secured to surface 19 by fastening means52. By pivoting sheet 50 about its hinge 51, the filter may be movedfrom the flat position (shown in solid line) to the viewing position(shown by dotted lines 50). Obviously, any other suitable arrangementmay be employed for both placement and configuration ofthe filterassembly.

The second system which may be employed consists of a projection systemand ground glass screen provided to produce an observable image. Thismethod has several significant advantages in that it is a fixed systemrequiring no operator attention and can be designed to magnify theimage, thereby producing a larger and more detailed picture of theoperation in progress. The uniqueness 'of the projection system lies inthe fact that the radiation employed for heating also provides theintense light necessary for magnification and projection. FIG. 4 showsthe projection system in which a por tion of the system of FIG. 2 isreproduced and further wherein like elements as between FIGS. 4 and 2are designated by like numerals. As shown therein, radiation source 10emits rays such as 14a and 1417 which impinge upon the reflectivesurface and are both reflected and focused as rays 15a and 15b, forexample. Reflector 12 is provided with an opening 53 to provide forvisual access of the projection system. A lens system 54 picks up lightreflected from the work surface and causes it to be focused upon aground glass 56 after having impinged upon and been reflected by aninverting mirror 55. The projection system components 54 through 56 maybe secured by any suitable bracketing or support means to the reflectorassembly so as to be fixed and moved with the reflector in the Zrdirection under control of manually operable handle 23 shown in FIG. 2.As such, the projection system is always capable of transmitting animage originating at the true focus of the heating system 13 without anyneed for further adjustment.

DETAILED DISCUSSION OF OPERATIONS PERFORMED Focused radiant heatingoffers unique advantages in the types of operations (especially in thedental preparation field) which the facility is capable of performing.Each will be discussed hereinbelow as regards their novel features andto further explain the significance of the facility describedhereinabove.

HIGH-TEMPERATURE SOLDERING As was stated previously, the joining ofcrowns to make a group implant is performed by high-temperaturesoldering. A filler alloy compatible with the cast metal is melted, and,with the proper fluxing agent, is allowed to wet the adjoining surfacesof the casting. This operation may be performed in air, in a reducingatmosphere, a neutral atmosphere, or in a vacuum.

One of the most vexing problems in soldering by conventional means isthe distortion which is found to occur if the joint structure is notuniformly heated. By this I mean that the periphery of the joint areamust experience simultaneous heating so that the thermal distortion isnormal to the surface being joined. In this manner, the crowns willreturn to their correct relative position upon cooling.

Focused radiant heating as described herein, has been found to producethe least possible joint distortion when compared to conventionalheating methods. The reason for this advantage is the fact that thejoint is simultaneously heated from multiple directions as a result ofboth direct and reflected rays originating from the irradiating means.The cone of incident energy impinging upon the work piece is typicallyof an ineluded angle which is greater than 120. By placing the workpiece inside the apex of the cone, all exposed surfaces of the jointsare caused to be uniformly heated.

Flame techniques, in which a single torch is employed, are capable ofheating onlyone side of the joint at once. Fanning, or moving, the torchwill improve this condition, but the control is still dependent upon theoperator's skill. Similarly, multiple torches may be used, but theoperation becomes cumbersome and difficult to set up.

A further advantage which accrues through the use of focused radiantheating lies in the fact that the work piece is completely free fromheater-borne contamination or disturbance. Thus, the joint is cleanerand more accurately controlled than that produced by any other method.

Most importantly, the method described herein is the only convenientmethod which may be employed for soldering in a vacuum. Furnacesoldering is a general heating method that indiscriminantly heats theentire structure. Resistance, induction and conduction methods allrequire elaborate set-ups with hardware provided in close proximity tothe joint and are, therefore, highly impractical arrangements ascompared with the apparatus of the present invention.

OVERLAY FIRING Overlays are applied to crowns for appearance and comfortto the wearer. They must be capable of withstanding all hazards thatnatural enamel is exposed to and must look and feel like the real tooth.

Ceramic overlays are the strongest and most durable types. They are alsothe most expensive and the most difficult to apply properly. The normalsequence in making an overlay starts with the technician brushing aslurry onto the prepared area of the crown. This slurry is typicallycomprised of ceramic particles suspended in an appropriatebinder-vehicle fluid. The application is performed in stages in order tobuild up to the proper thickness of coating and further in order toachieve the correct coloring and texture. Between each application, thecrown is fired to fuse the ceramic. All presently available methodsemployed for fusing have been found to take 15 minutes, or longer. This,obviously, extends the operation (from start to finish) to a ratherprolonged time period, especially when a number of overlay applicationsare required- It is necessary to fuse between application operationsbecause conventional heating is performed by conduction. The surface ofthe overlay cannot be allowed to fuse together and form a skin beforethe underlaying slurry is fused. Skinning will cause entrapment of gasesand delamination of the overlay. The limit of the skin formation, ofcourse, is the maximum thickness of material that may be applied at onetime. I

Conductive heating is the primary mode of energy transfer even thoughthe ceramic is often fired in a vacuum using infrared radiation. Theconventional firing furnace utilizes long wavelength infrared radiation,the bulk of which is readily absorbed by ceramic or glassy materials.The absorption takes place in the first few thousandths of an inch ofthe material. Any deeper heating penetration must be conducted throughthe remaining thickness and into the crown metal.

The reason for employing a skin formation technique is that conductiveheating requires a thermal gradient for energy transfer. Since theenergy must pass through the overlay material, the thermal gradient hasa negative slope (i.e., reduces in thermal level from the surface of theoverlay material to the inner depth thereof), the surface of the overlaymaterial is, therefore, always at a higher temperature level than theunderlying material until equilibrium is reached.

, Focused radiant heating which employs a high-intensity source ofradiating energy, the bulk of which is comprised of wavelengths shorterthan 2.80 microns, is capable of penetrating the commonly used ceramicslurries. This permits a high percentage of the energy to be absorbed atthe metal-ceramic interface, thus causing the underlayments to be heatedby conduction from the inside outwardly. Actually, the combination ofheating by radiation transmission losses and inside-out conductivetransfer causes the overlay to melt simultaneously throughout its entirethickness.

An immediate consequence of this capability of being able to heat deeplywithin an overlay is that the full required thickness of overlay can beapplied in a single operation. An experienced technician can even applystaining and coloring ingredients before the first firing. The entireoperation can thus be reduced to a single firing requiring an elapsedtime of no more than 1 to 2 minutes duration.

INVESTMENT CASTING In the investment casting of crowns, less than 1ounce of metal is typically melted at one time. Employing thistechnique, it is within the capability of small, focused radiant heatingdevices having energy sources of 1,000 to 2,000 watt capacity. Inaddition, it is most desirable to perform the moldfilling operation in avacuum. These criteria plus the inherently clean and simple operation offocused heating apparatus makes investment casting an ideal operation tobe performed through the use of the apparatus described herein.

Referring to FIG. 5, in which like elements are designated with likenumerals'in regard to FIGS. 2 and 3, the prepared mold 66 is placed uponwork plate 34. A crucible holder 67 supports a crucible 68 which ispositioned immediately above mold 66 so that the crucible lies over thefilling hole 69 of mold 66. The crucible 68 is formed of two sections68a and 68b which are pivoted about a pivot pin 70 further secured tocrucible holder 68 so as to permit the crucible sections 68a and 68b torotate in opposing directions and thereby open at the bottom. When thecharge provided in crucible 68 is heated to the correct temperaturelevel, the crucible is opened remotely by mechanical means (not shown)mechanically linking the crucible halves to an externally mountedcontrol handle. Obviously, this mechanical configuration may take anyone of a number of preferred forms, depending only upon the needs of theuser, and a detailed description has been omitted herein for purposes ofsimplicity.

. into the opening in the mold member 66. Obviously, the press Thecrucible is thus opened remotely and the charge is thus caused to fallby gravity into the opening 69 of mold 66. The remote opening functionmaybe performed, for example, by magnetic actuation, or by mechanicalmeans extending through the work plate 34. Alternatively, the cruciblemay be designed so as to tip about its pivot pin to provide a pouringaction or may further be designed to have a removable plug at its bottomend, whereby the end result is the same regardless of the specifictechnique employed.

Crucible 68 is preferably formed of a ceramic, quartz, carbon, orvitreous carbon material. The lattermost material is preferred due toits durability and high-temperature strength. In addition, its blackcolor allows it to be readily heated by focused radiation represented byrays 15a and 15b, for example. It is thus clear from this descriptionthat investment casting operations can utilize the apparatus of thepresent invention with the same high degree of success as was describedwith regard to some of the operations set forth hereinabove.

FIG. 7 shows a portion of the apparatusof FIG. wherein an assembly isprovided for pivoting the crucible halves 68a and 68b. As shown in FIG.7, a hollow conduit 91 is mounted along the exterior of crucible supportmember 67 such as, for example, by brackets 67a, 67b and 67c. The lowerend of conduit 91 is coupled to an opening 92 in work plate 34 by acoupler assembly 93. The opposite end of opening 92 is coupled through aconduit 94 and valve 95 to a pressure source 96 which may be an air orhydraulic means. The upper end of conduit 91 is coupled to a T-shapedmember 97 having a pair of pistons 98 and 99 mounted therein andprotruding in opposing directions. The crucible halves 68a and 68b areprovided with projections 100 and 101 which lie immediately adjacent thefree ends of piston members 98 and 99, respectively.

In operation, when the material contained within the crucible iselevated to the desired temperature, valve means 95 is opened to forceeither air or a liquid under pressure through conduit 94, opening 92 andconduit 91 so as to cause the pistons 98 and 99 to both move outwardlyagainst the projection 100 and 101, respectively, to cause the cruciblehalves 68a and 68b, which are pivoted at 70, to rotate in opposingdirections and thereby cause the molten charge contained with thecrucible to drop downwardly, as shown by arrow 102,

sure or hydraulic arrangement may be replaced by a mechanicalarrangement adapted to perform substantially thesame function. I FIG. 7ashows another preferred embodiment of the crucible arrangements of FIGS.5 and 7 in which the two crucible halves 68a and 68b are each providedwith a semicircular shaped ledge 68c and 68d, respectively. Each ofthese ledges is supported by a pair of knife-edge pivots 110 and 111(only one knife-edge pivot of each of the pairs being shown in FIG. 7ait being understood that the other knife-edge pivot of each pair ispositioned on the opposite sides of the crucible halves). The knife-edgepivots may be supported by a supporting structure similar to thesupporting structure 67, shown in FIG. 5. The pivots are arranged tosupport the crucible flanges 68c and 68d so as to cause the cruciblehalves to pivot in the directions shown by arrows 112 and 113,respectively, so long as no means is provided for holding the cruciblehalves together. The crucible halves are provided with hollow interiorsfor supporting a charge of material to be heated to the .molten stage.Each crucible half is provided with an opening 114 and 115 near theirlower edges, which openings are in alignment with one another. A fusibleelement 116, such as, for example, a thin wire, is inserted through thealigned openings 114 and 115. The free ends 116a and 1161) are bentinwardly as shown so as to hold the crucible halves together until thefusible element melts, at which time the crucible halves are free topivot about the knife-edged pivots 110 and ill in the directions shownby arrows ll} and H3, rcspeu in operation. the heating source comprisedof a radiant energy source and reflector l2 (see FIG. 5) focuses radiantelevated in temperature as a result of the impinging radiant energy. Theheating of the crucible and charge of material from the top causes thetemperature gradient to extend from the top downward with the top of thecrucible being at the highest temperature, thereby causing the fusibleelement to be the last component to be raised to the desired elevatedtemperature. The advantage of employing infrared energy is derived fromthe fact that infrared radiant energy is a known constant source ofenergy and provides substantially homogenous and uniform heating of thematerial. The fusible element may be selected by determining thetemperature gradient existing between the molten charge and the regionin which the fusible element is positioned (openings 116a and 116b). Byknowing this temperature gradient, a fusible element can be selectedwhich will melt at its center location only after the molten charge hasbeen elevated to the desired temperature. Since the center portion ofthe fusible element will melt and cause separation of the cruciblehalves 68a and 68b prior to the melting of the remaining portions of thefusible element, the fusible element will be restrained from droppinginto the mold or other container into which the molten charge isdispensed. The advantage of the use of a radiant energy source can befurther appreciated from a consideration of the disadvantages of otherheating sources. For example, a heating torch will fail to provideuniform homogeneous heating of the molten charge and will therefore failto cause melting of the fusible element at the appropriate temperaturelevel. The use of an induction heating apparatus is unsatisfactory forthe reason that induction heating equipment tends to heat only metalcomponents, thereby causing the fusible element to heat too rapidlybefore heating of the molten charge to the appropriate temperaturelevel.

It can, therefore, be seen from the foregoing description that thepresent invention provides a novel apparatus and method for heatingmaterials through the use of a radiation source wherein the heating zoneof the material to be so treated may be rapidly and accuratelypositioned within the major zone of influence of the heating apparatus,wherein the heating zone may be easily and carefully observed to controlthe parameters of time and temperature and wherein the heating operationitself is performed in a more uniform manner as compared withconventional techniques. The descriptions set forth hereinabove make itquite obvious that the apparatus and method set forth herein are highlyadvantageous for use in the dental field.

Although this invention has been described with respect to its preferredembodiments, it should be understood that many variations andmodifications will now be obvious to those skilled in the art, and it ispreferred, therefore, that the scope of the invention be limited not bythe specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. Apparatus for rapidly and accurately heating specified regions of awork piece comprising: e

a heating assembly including a source of radiant energy, and

a reflector member having a reflective surface for focusing reflectedradiation from said source at a predetermined true image focal zone;

a mechanical pointer assembly mounted upon said heating assembly;

a supporting surface;

a supporting assembly, coupled to said heating assembly positioned uponsaid supporting surface;

said supporting assembly including means for adjusting the relativedistance between said heating assembly and said supporting surface;

it first movable plate and means positioned upon said supporting surfacefor constraining movement of said movable plate along an imaginarystraight line which is substantially parallel to said supportingsurface:

i it said mechanical point or assembly including an arm having a pointertip at its free end; said pointer tip and said true image focal zonelying in an imaginary line parallel to said imaginary path ofconstrained movement of said first plate;

first and second mechanical stop means positioned in the path ofmovement of said first movable plate to limit the movement of said firstmovable plate between first and second positions, respectively;

a second movable work plate and means positioned between said first andsecond movable plates to enable said second movable plate to experiencemovement in the common plane between the plates which is substantiallyparallel to said supporting surface;

the amount of allowable travel between. said first and second stopmembers being substantially equal to the distance between the pointertip of said mechanical pointer and said image focal zone measured insaid horizontal plane.

the upper surface of said second movable plate being adapted to supporta work piece whereby adjustment of said second movable plate and saidmechanical pointer to position the specified region of the work piece tobe heated immediately beneath the extreme tip of the mechanical pointerprecisely locates the region of the work piece to be heated within animaginary focal zone when the first movable plate is moved against saidfirst stop member which preparatory adjustment exactly locates theregion of the work piece to be heated in the true image focal zone whensaid first movable plate is subsequently moved against said second stopmember.

2. Apparatus for rapidly and accurately heating specified regions ofawork piece comprising:

a heating assembly including a source of radiant energy, and

a reflector member having a reflective surface for focusing reflectedradiation from said source at a predetermined true image focal zone;

a mechanical pointer assembly mounted upon said heating assembly;

a supporting surface;

a supporting assembly coupled to said heating assembly positioned uponsaid supporting surface;

said supporting assembly including means for adjusting the relativedistance between said heating assembly and said supporting surface; I

said mechanical pointer assembly including an arm having a pointer tipat its free end;

a movable plate and means positioned upon said supporting surface forconstraining movement of said movable plate along a first imaginarystraight line which is substantially parallel to said supportingsurface;

first and second alignment means positioned in the path of movement ofsaid movable plate to limit the movement of said movable plate betweenfirst and second positions, respectively;

the pointer tip of said mechanical pointer free end being positioned tolie in a second imaginary straight line containing said true image focalzone to define an imaginary image focal cone, said fist and secondimaginary straight lines being parallel;

the amount of allowable travel between said first and second stopmembers being substantially equal to the distance between the pointertip of said mechanical pointer and said image focal zone measured alongsaid second imaginary straight line;

the upper surface of said movable plate being adapted to support a workpiece whereby positioning of the work piece on said movable plate andadjustment of said mechanical pointer to position the specified regionof the work piece to be heated immediately beneath the extreme tip ofthe mechanical pointer precisely locates the region of the work piece tobe heated within an imaginary focal zone when the movable plate is movedagainst said first stop member, which preparatory adjustment exactlylocates the region of the work piece to be heatedin the true image focalzone when said movable plate is subsequently moved against said secondstop member.

3. The apparatus of claim 1 further including gasket means positionedbetween the adjacent upper and lower surfaces of said first and secondmovable plates, respectively;

a vacuum source;

a conduit connected to said vacuum source;

said first movable plate having a hollow opening, said opening having afirst end communicating with the upper surface of said first movableplate and within the confines of said gasket, and having a second endcommunicating with said conduit for evacuating the interior regiondefined by said gasket and said first and second movable plates torigidly hold the first and second movable plates in their relativepositions.

4. The apparatus of claim 2 wherein said constraining means comprises atleast one rail mounted upon said supporting surface;

a guide channel formed in the underside of said first movable plate forslidably receiving said rail.

5. The apparatus of claim 2 wherein said constraining means comprisesfirst and second rails mounted upon said supporting surface;

first and second guide channels formed in the under-side of said firstmovable plate for slidably respectively receiving said first and secondrails.

6. The apparatus of claim 2 wherein said constraining means is comprisedof an elongated groove provided in said supporting surface;

' said first movable plate having an elongated projection along itsbottom surface being slidably mounted within said groove.

7. The apparatus of claim 2 wherein said constraining means is comprisedof first and second elongated grooves provided in said supportingsurface;

said first movable plate having first and second elongated projectionsalong its bottom surface being slidably mounted within said first andsecond grooves, respectively.

8. The apparatus of claim 2 wherein said mechanical pointer assembly iscomprised of a mounting bracket secured to said heating assembly;

an elongated arm having a first end releasably coupled to said mountingbracket; the pointer tip being mounted upon the free end of said arm.

9. The apparatus of claim 2 wherein said mechanical pointer assembly iscomprised of a mounting bracket secured to said heating assembly;

an elongated arm having a first end pivotally coupled to said mountingbracket; the pointer tip being mounted upon the free end of said am.

10. The apparatus of claim 9 wherein said arm further comprises meanscoupled to said mounting bracket for adjusting the location of saidpointer tip relative to said heating assembly.

11. The apparatus of claim 2 further comprising a vacuum source and aconduit having a first end coupled to said vacuum source; 7

said first movable plate being provided with a hollow opening having afirst end communicating with the upper surface of said first movableplate and a second opening communicating with the second end of saidconduit;

said first movable plate having a continuous closed loop groove providedin its upper surface; a resilient gasket positioned in said groove;

a bell jar positioned upon the upper surface of said first movable plateand having its periphery resting upon said gasket to enable the interiorregion defined by said bell jar and the upper surface of said firstmovable plate to be evacuated by said vacuum source.

12. The apparatus of claim 11 wherein said bell jar is formed of aradiant energy transmissive material.

Q13. The apparatus of claim 11 further comprising:

a reservoir containing a gas under pressure; and a second conduit havinga fist end connected to said reservoir;

said first movable plate being provided with a second open ing having afirst end communicating with the upper surface of said first movableplate and a second end communicating with the second end of said secondconduit;

adjustable valve means being provided in said second coriduit betweensaid reservoir and said first movable plate to adjust the amount of gasintroduced into the evacuated region. 14. The apparatus of claim 2further having projection apparatus comprising:

a focusing leans positioned a spaced distance from said work piece;

an image forming display surface;

an inverting mirror for deflecting reflected light rays passing throughsaid focusing lens and originating from said work piece upon saiddisplay surface whereby said focusing lens focuses the reflected lightoriginating from said work piece upon said display surface. 15. Theapparatus of claim 14 wherein said projection apparatus is mounted tosaid heating assembly so as to have the distance apart to substantiallydefine the end points or" said elongated line image.

i il

1. Apparatus for rapidly and accurately heating specified regions of awork piece comprising: a heating assembly including a source of radiantenergy, and a reflector member having a reflective surface for focusingreflected radiation from said source at a predetermined true image focalzone; a mechanical pointer assembly mounted upon said heating assembly;a supporting surface; a supporting assembly, coupled to said heatingassembly positioned upon said supporting surface; said supportingassembly including means for adjusting the relative distance betweensaid heating assembly and said supporting surface; a first movable plateand means positioned upon said supporting surface for constrainingmovement of said movable plate along an imaginary straight line which issubstantially parallel to said supporting surface; said mechanical pointor assembly including an arm having a pointer tip at its free end; saidpointer tip and said true image focal zone lying in an imaginary lineparallel to said imaginary path of constrained movement of said firstplate; first and second mechanical stop means positioned in the path ofmovement of said first movable plate to limit the movement of said firstmovable plate between first and second positions, respectively; a secondmovable work plate and means positioned between said first and secondmovable plates to enable said second movable plate to experiencemovement in the common plane between the plates which is substantiallyparallel to said supporting surface; the amount of allowable travelbetween said first and second stop members being substantially equal tothe distance between the pointer tip of said mechanical pointer and saidimage focal zone measured in said horizontal plane. the upper surface ofsaid second movable plate being adapted to support a work piece wherebyadjustment of said second movable plate and said mechanical pointer toposition the specified region of the work piece to be heated immediatelybeneath the extreme tip of the mechanical pointer precisely locates theregion of the work piece to be heated within an imaginary focal zonewhen the first movable plate is moved against said first stop memberwhich preparatory adjustment exactly locates the region of the workpiece to be heated in the true image focal zone when said first movableplate is subsequently moved against said second stop member. 2.Apparatus for rapidly and accurately heating specified regions of a workpiece comprising: a heating assembly including a source of radiantenergy, and a reflector member having a reflective surface for focusingreflected radiation from said source at a predetermined true image focalzone; a mechanical pointer assembly mounted upon said heating assembly;a supporting surface; a supporting assembly coupled to said heatingassembly positioned upon said supporting surface; said supportingassembly including means for adjusting the relative distance betweensaid heating assembly and said supporting surface; said mechanicalpointer assembly including an arm having a pointer tip at its free end;a movable plate and means positioned upon said supporting surface forconstraining movement of said movable plate along a first imaginarystraight line which is substantially parallel to said supportingsurface; first and second alignment means positioned in the path ofmovement of said movable plate to limit the movement of said movableplate between first and second positions, respectively; the pointer tipof said mechanical pointer free end being positioned to lie in a secondimaginary straight line containing said true image focal zone to definean imaginary image focal cone, said fist and second imaginary straightlines being parallel; the amount of allowable travel between said firstand second stop members being substantially equal to the distancebetween the pointer tip of said mechanical pointer and said image focalzone measured along said second imaginary straight line; the uppersurface of said movable plate being adapted to support a work piecewhereby positioning of the work piece on said movable plate andadjustment of said mechanical pointer to position the specified regionof the work piece to be heAted immediately beneath the extreme tip ofthe mechanical pointer precisely locates the region of the work piece tobe heated within an imaginary focal zone when the movable plate is movedagainst said first stop member, which preparatory adjustment exactlylocates the region of the work piece to be heated in the true imagefocal zone when said movable plate is subsequently moved against saidsecond stop member.
 3. The apparatus of claim 1 further including gasketmeans positioned between the adjacent upper and lower surfaces of saidfirst and second movable plates, respectively; a vacuum source; aconduit connected to said vacuum source; said first movable plate havinga hollow opening, said opening having a first end communicating with theupper surface of said first movable plate and within the confines ofsaid gasket, and having a second end communicating with said conduit forevacuating the interior region defined by said gasket and said first andsecond movable plates to rigidly hold the first and second movableplates in their relative positions.
 4. The apparatus of claim 2 whereinsaid constraining means comprises at least one rail mounted upon saidsupporting surface; a guide channel formed in the underside of saidfirst movable plate for slidably receiving said rail.
 5. The apparatusof claim 2 wherein said constraining means comprises first and secondrails mounted upon said supporting surface; first and second guidechannels formed in the under-side of said first movable plate forslidably respectively receiving said first and second rails.
 6. Theapparatus of claim 2 wherein said constraining means is comprised of anelongated groove provided in said supporting surface; said first movableplate having an elongated projection along its bottom surface beingslidably mounted within said groove.
 7. The apparatus of claim 2 whereinsaid constraining means is comprised of first and second elongatedgrooves provided in said supporting surface; said first movable platehaving first and second elongated projections along its bottom surfacebeing slidably mounted within said first and second grooves,respectively.
 8. The apparatus of claim 2 wherein said mechanicalpointer assembly is comprised of a mounting bracket secured to saidheating assembly; an elongated arm having a first end releasably coupledto said mounting bracket; the pointer tip being mounted upon the freeend of said arm.
 9. The apparatus of claim 2 wherein said mechanicalpointer assembly is comprised of a mounting bracket secured to saidheating assembly; an elongated arm having a first end pivotally coupledto said mounting bracket; the pointer tip being mounted upon the freeend of said arm.
 10. The apparatus of claim 9 wherein said arm furthercomprises means coupled to said mounting bracket for adjusting thelocation of said pointer tip relative to said heating assembly.
 11. Theapparatus of claim 2 further comprising a vacuum source and a conduithaving a first end coupled to said vacuum source; said first movableplate being provided with a hollow opening having a first endcommunicating with the upper surface of said first movable plate and asecond opening communicating with the second end of said conduit; saidfirst movable plate having a continuous closed loop groove provided inits upper surface; a resilient gasket positioned in said groove; a belljar positioned upon the upper surface of said first movable plate andhaving its periphery resting upon said gasket to enable the interiorregion defined by said bell jar and the upper surface of said firstmovable plate to be evacuated by said vacuum source.
 12. The apparatusof claim 11 wherein said bell jar is formed of a radiant energytransmissive material.
 13. The apparatus of claim 11 further comprising:a reservoir containing a gas under pressure; and a second conduit havinga fist end connected to said reservoir; said first movable Plate beingprovided with a second opening having a first end communicating with theupper surface of said first movable plate and a second end communicatingwith the second end of said second conduit; adjustable valve means beingprovided in said second conduit between said reservoir and said firstmovable plate to adjust the amount of gas introduced into the evacuatedregion.
 14. The apparatus of claim 2 further having projection apparatuscomprising: a focusing leans positioned a spaced distance from said workpiece; an image forming display surface; an inverting mirror fordeflecting reflected light rays passing through said focusing lens andoriginating from said work piece upon said display surface whereby saidfocusing lens focuses the reflected light originating from said workpiece upon said display surface.
 15. The apparatus of claim 14 whereinsaid projection apparatus is mounted to said heating assembly so as tohave the work piece constantly in focus regardless of the adjustment ofsaid heating assembly.
 16. The apparatus of claim 2 wherein said heatingapparatus is adapted to form an elongated line image of radiant energy;said pointer tip being an elongated line tip defining an imaginary lineimage substantially equal in length to said line image.
 17. Theapparatus of claim 2 wherein said heating apparatus is adapted to forman elongated line image of radiant energy; said pointer tip beingcomprised of first and second end points defining an imaginary lineimage arranged a spaced distance apart to substantially define the endpoints of said elongated line image.